Continuity mistake: When Lila is finishing her first joke, Rhonda suddenly switches from her French outfit to her "usual" one; also, during the Jell-O incident, her beret disappears and then reappears.
Continuity mistake: In "Miss Perfect", Helga, Rhonda, Sheena, Phoebe, and Nadine are cooking up ways to make Lila's (the new girl) life miserable. In one shot, Rhonda is wearing her new blue outfit. When the scene cuts to the boys and Lila, and then back to the five girls, Rhonda is wearing her standard red sweater and black pants. For the rest of that day, she is back in her new outfit.
Continuity mistake: Ms. Perfect: When Lila goes to Patty's locker, the books she is holding constantly change. First, she is holding two books, then three, then the red book is suddenly on top, then the red book disappears and the rectangle on the brown book changes to white, then it goes back to yellow and the blue book gets replaced by the red one, and finally, the blue book reappears (she is also suddenly not holding the locker handle, and the way she holds the books changes). (00:15:48)
Continuity mistake: Ms. Perfect: When Patty opens her locker and the jello falls on her, her head is raised above the floor, and there is no jello on her head. In the next shot, her head is on the floor, and there is jello on her head. (00:16:24)
Continuity mistake: Ms. Perfect: The red strings attached to Lila's table and chair are only there as Lila is getting pranked; they are not visible in any other shot of the table. Also, when Rhonda pulls the string attached to the table, the string attached to the chair isn't there. (00:18:32)
Continuity mistake: Ms. Perfect: When the girls prank Lila, the table has its flap down, there are four chairs around it, and there is nothing on it. When Helga walks Lila over to the table, the flap is up, there are only two chairs around it, and a "Reserved" card appears on it. When Lila runs out of the cafeteria, there are four chairs around the table again. (00:18:06 - 00:18:48)
Continuity mistake: Ms Perfect: When Lila is wearing her new blue outfit at recess, she wears light blue bows in her braids, but when she is shown in close-up, she is wearing her regular green bows. There is also a small animation glitch with Lila's right bow. (00:15:22)
Continuity mistake: Ms. Perfect: When the flap on Lila's table falls down, her lunch bag falls over. When the tray of spinach and fish falls on her, it changes position. (00:18:37)
Answer: The show is based in present day times. Plus most cars aren't old fashtioned, I recall seeing a limo and not to mention a cherry picker, etc.